<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /* 通配符选择器 */
    * {
      color: red;
    }
  </style>
</head>

<body>
  <h1>Hello world!</h1>
  <h2>Hello world!</h2>
  <h3>Hello world!</h3>
  <h4>Hello world!</h4>
  <h5>Hello world!</h5>
  <h6>Hello world!</h6>
</body>

</html>